Optical device having a deformable optical element

ABSTRACT

The disclosure relates to an optical device, in particular for microlithography. The optical device includes an optical module and a support structure that supports the optical module. The optical module includes an optical element and a holding device that holds the optical element. The holding device includes a deformation device having a plurality of active deformation units which contact the optical element and which are designed so as to impose a pre-defined deformation on the optical element. The optical module is fixed to the support structure in a replaceable manner.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of, and claims benefit under 35 USC120 to, international application PCT/EP2009/058943, filed Jul. 14,2009, which claims benefit of German Application No. 10 2008 032853.7-51, filed Jul. 14, 2008 and U.S. Ser. No. 61/080,423, filed Jul.14, 2008. International application PCT/EP2009/058943 is herebyincorporated by reference in its entirety.

FIELD

The present disclosure relates to optical devices, optical imagingdevices including such an optical device, a set of components for suchan optical device, and a method for supporting an optical element. Thedisclosure may be applied in connection with any desired optical devicesor optical imaging methods. In particular, it may be applied inconjunction with microlithography as used during the production ofmicroelectronic circuits.

BACKGROUND

Apart from using components that are implemented with a level ofprecision as high as possible, it is desirable, particularly in the areaof microlithography, to adjust the position and geometry of opticalmodules of the imaging device, i.e. for example of the modules havingoptical elements such as lenses, mirrors or gratings, but also of themasks and substrates used, during operation as precisely as possible inaccordance with specified setpoint values or to keep such components intheir position once adjusted, in order to achieve a correspondingly highimaging quality (whilst the term optical module, in terms of the presentdisclosure, is to encompass both optical elements alone and assembliesmade of such optical elements and further components, such as forexample frame parts etc.).

In the area of microlithography, the desired level of precision is inthe microscopic range in the order of just a few nanometres or less.They are not least a consequence of the constant desire to enhance theresolution of the optical systems used for the manufacture ofmicroelectronic circuits, in order to advance the miniaturisation of themicroelectronic circuits to be produced.

In this connection it is known, amongst others, from US 2003/0234918 A1(Watson), US 2007/0076310 A1 (Sakino et al.), U.S. Pat. No. 6,803,994 B1(Margeson), DE 198 59 634 A1 (Becker et al.) as well as DE 101 51 919 A1(Petasch et al.), the respective disclosures of which are incorporatedherein by reference, to impose pre-defined deformations on individual ora plurality of optical elements of the system, in order to correctimaging errors of the imaging device. The deformation of the opticalelement concerned is here not only used to correct the respectiveoptical element itself, but rather this is done in an attempt tocompensate also for errors in the wave front, which are introduced byother components of the imaging device.

What can be problematic here is that the optical elements activelydeformed in order to correct imaging errors as well as the othercomponents involved in the deformation are not only exposed duringoperation to the usual thermal and dynamic loads, but, as a result ofthe deformation, also to further, partially substantial dynamic loads.These additional loads can have a negative effect on the lifetime of theoptical element or of the other components involved in the deformation.Accordingly, these components of the imaging system generally aredesigned to be correspondingly robust and/or complex in order to meetthe desired lifetime for the overall system. Moreover, optical elementshaving a larger cross section usually will have to be deformed. This inturn means that the actuators used are generally designed in such a waythat forces that are appropriately high for a sufficient deformation areachieved.

A further problem, for example, in connection with the system known fromUS 2003/0234918 A1 (Watson) is that force actuators (for example Lorentzactuators) are used to generate the deformation, which force actuatorsthemselves have a very low rigidity in their actuation direction andmoreover act on the optical element via a system that is soft in theforce flux direction, so that for small deformations of the opticalelement, comparatively long travel ranges are generally desired. As aresult, a comparatively large installation space is generally desiredfor the deformation device, which can be of disadvantage in the light ofthe usually already confined spaces available.

A further disadvantage in connection with the known imaging systems canlie in the fact that, for the deformation of the optical elementsconcerned, a design of the support structure for the optical elementwhich is specially adapted for this purpose is used. This means, ifthere is a wish to provide, in a pre-existing or fully designed opticalimaging system, an optical element that has so far not been providedwith such an active deformation with a corresponding deformationfacility, then this will, as a rule, involve a complete re-design of thesupport structure for the optical element. This may, in certaincircumstances, have an effect on the entire imaging system, if it is notpossible to keep the position and the orientation of the optical elementunchanged within the imaging system.

A further disadvantage of the imaging systems already known for examplefrom US 2007/0076310 A1 (Sakino et al.) can lie in the fact that a quicksuccess of the correction of imaging errors is largely dependent on thedynamic mechanical properties of the components involved in thedeformation. Here, it is in principle particularly advantageous from adynamic point of view if, amongst other things, the support structurethat supports the deformation forces is designed to be particularlyrigid (ideally infinitely rigid). The reason is that, in this case, arelative independence of the actuating movements of the individualactuators will be ensured, whereas the actuating movements of anactuator in the case of a less rigid support structure result in adeformation of the support structure, which influences the position andthe orientation of at least the adjacent actuators, which in turninvolves a correction within their region. As a result, a very complexcontrol concept can become desirable, which can meet the desired dynamicproperties in the field of microlithography only to a limited extent.

SUMMARY

The present disclosure provides an optical device, an optical imagingdevice, a method for supporting the optical element and/or a set ofcomponents for an optical device, which enable in particular in a simplemanner the application of an active deformation of one or more opticalelements so as to achieve a rapid correction of imaging errors, in orderto achieve an imaging quality that is permanently as high as possibleduring operation with a throughput as high as possible.

The present disclosure is on the one hand based on recognizing that anactive deformation of one or more optical elements, a rapid correctionof imaging errors and, thus, a particularly high imaging quality may beachieved on a permanent basis in a simple manner with a high throughputby designing the optical module including the optical element to bedeformed to be replaceable in an easy manner. In the context of thepresent disclosure, easy replaceability is to be understood to mean,amongst other things, that optical modules can, if desired, be replacedeven with just a brief interruption of the operation of the entireoptical imaging device. This replaceability of the optical module allowsa correspondingly simpler and/or lighter design of the optical module.Although it may then be possible that the optical module no longerachieves the desired lifetime of the overall imaging device, but this isnot critical by virtue of the fact that the optical module and thus theoptical element are replaceable.

The simpler and lighter design of the optical module moreover allowsinstallation space for the connection mechanism to be freed, whichensure a simple connection and/or disconnection and thus thereplaceability of the optical module, so that it becomes possible tointegrate the optical module into an existing design of an opticalimaging system without having to modify the connection dimensions of theremaining imaging system.

The lighter design of the optical module in turn may also have apositive effect on the dimensioning of the deformation device of theoptical module, which deforms the optical element. As a result itbecomes advantageously possible to integrate such an optical modulehaving an actively deformable optical element within a confinedinstallation space. In particular it is even possible in the case of aspecified design of the imaging system, to use such an active moduleinstead of the former passive module (without such an active deformationof the optical element), without having to (substantially) modify theremaining design of the optical imaging system.

According to a first aspect, the present disclosure therefore relates toan optical device, in particular for microlithography, which includes anoptical module and a support structure, the support structure supportingthe optical module. The optical module includes an optical element and aholding device, the holding device holding the optical element. Theholding device includes a deformation device having a plurality ofactive deformation units which contact the optical element and which aredesigned to impose a pre-defined deformation on the optical element. Theoptical module is fixed to the support structure in a replaceablemanner.

According to a further aspect, the present disclosure relates to amethod for supporting an optical element, in particular formicrolithography, wherein the optical element is held by a holdingdevice of an optical module and the optical module is supported by asupport structure, with a pre-defined deformation being imposed on theoptical element by a plurality of active deformation units and theoptical module being held by the support structure in a replaceablemanner.

According to a further aspect, the present disclosure relates to a setof components for an optical device, in particular for microlithography,including an optical module and a support structure, the supportstructure supporting the optical module in a first condition of theoptical device. The optical module includes an optical element and aholding device, the holding device holding the optical element. Theholding device includes a deformation device having a plurality ofactive deformation units which contact the optical element and which aredesigned to impose a pre-defined deformation on the optical element. Theoptical module is fixed to the support structure in a replaceable mannervia at least one supporting point. Further, an optical replacementmodule is provided, the optical replacement module being designed totake the place of the optical module in a second condition of theoptical device and to be fixed to the support structure via the at leastone supporting point.

The present disclosure is further based on recognizing that it isparticularly advantageous to use actuators for the deformation of theoptical element, which have a high rigidity in their actuation direction(i.e. in the direction in which they generate a force or a momentum).This design has the advantage that actuators having such rigidity as arule have a compact size and, if appropriate, short travel ranges with ahigh resolution of the travel range, so that the deformation device onlyinvolves a comparatively small installation space. As has already beenexplained above, this makes it possible to integrate such an opticalmodule having an actively deformable optical element within a confinedinstallation space. In particular it is even possible, with a specifieddesign of the imaging system, to use such an active module instead ofthe former passive module (without such an active deformation of theoptical element), without having to (substantially) modify the remainingdesign of the optical imaging system.

In this connection it is particularly advantageous to implement thestructure that supports the respective deformation device also to be asrigid as possible, in order to keep any mutual influences amongst theindividual deformation devices and, thus, the complexity of the controlof the active deformation of the optical element as low as possible.However, it will be understood that in certain variants of thedisclosure it may also be provided for a correspondingly complex controlsystem to be realised, which compensates for these mutual influences viaa suitable control concept and a sufficient control bandwidth.

According to a further aspect, the present disclosure therefore relatesto an optical device, in particular for microlithography, including anoptical module and a support structure, the support structure supportingthe optical module. The optical module includes an optical element and aholding device, the holding device holding the optical element. Theholding device includes a deformation device having a plurality ofactive deformation units which contact the optical element and which aredesigned to impose a pre-defined deformation on the optical element viaa deformation force in a deformation force direction. The holding devicefurther includes a positioning device including at least one, inparticular active, positioning unit which contacts the optical elementand which is designed to adjust the position and/or the orientation ofthe optical element. At least one of the deformation units includes anactuator unit for generating the deformation force, with the actuatorunit generating a force or a momentum in an actuation direction andhaving a high rigidity in the actuation direction.

According to a further aspect, the present disclosure relates to amethod for supporting an optical element, in particular formicrolithography, wherein the optical element is held by a holdingdevice of an optical module and the optical module is supported by asupport structure, the optical element being contacted by a plurality ofactive deformation units of a deformation device of the holding deviceand each deformation unit imposing a pre-defined deformation on theoptical element via a deformation force in a deformation forcedirection. The optical element is contacted by at least one positioningunit of the holding device, the at least one positioning unit adjustingthe position and/or the orientation of the optical element. Therespective deformation force is generated by an actuator unit of thedeformation units, the actuator unit generating a force or a momentum inan actuation direction and having a high rigidity in the actuationdirection.

The present disclosure is further based on recognizing that a simpleintegration of an active deformation of one or more optical elementswith the advantages resulting therefrom is also possible with apre-existing design of the imaging system, if a deformation devicehaving a separate (from the holding structure of the respective opticalelement) abutment structure is provided which on the holding structureof the respective optical element. As a result, it is in particularpossible to retrofit such a deformation device in a simple manner,without having to carry out any significant modifications to the opticalelement of our holding structure.

According to a further aspect, the present disclosure relates to anoptical device, in particular for microlithography, including an opticalelement and a holding device, the holding device having a holdingstructure that holds the optical element. The holding device includes adeformation device having a plurality of active deformation units whichcontact the optical element and which are designed to impose apre-defined deformation on the optical element. The deformation devicehas an abutment structure that is separate from the holding structure,the abutment structure being fixed, in particular in a detachablemanner, to the holding structure and at least one of the deformationunits being supported on the abutment structure.

According to a further aspect, the present disclosure relates to amethod for supporting an optical element, in particular formicrolithography, wherein the optical element is held by a holdingstructure of a holding device and a pre-defined deformation is imposedon the optical element by a plurality of active deformation units of adeformation device of the holding device. To this end, an abutmentstructure of the deformation device, which is separate from the holdingstructure, is fixed, in particular in a detachable manner, to theholding structure and at least one of the deformation units is supportedon the abutment structure.

Finally, the present disclosure is based on recognizing that the desiredactive deformation may be realised by an active deformation device of aparticularly compact design, which may optionally be integrated into anexisting design of the imaging system in a simple manner, if a separatemeasuring device is provided which measures the deformation of theoptical element. By using such a measuring device it becomes possible,amongst other things, to impose displacements instead of forces on theoptical element concerned by the deformation units of the deformationdevice. Although the desired control algorithm becomes more complex as aresult of the mutual influences of the individual deformation units,which are inherent to such a solution (a displacement generated by oneof the deformation units entails another displacement at least in theregion of adjacent deformation units), but the measuring device enablessuch a control to be realised with a sufficient control bandwidth.

According to a further aspect, the present disclosure therefore relatesto an optical device, in particular for microlithography, including anoptical element and a holding device, the holding device including aholding structure that holds the optical element, in particular in astatically determined manner. The holding device includes a deformationdevice having a plurality of active deformation units which contact theoptical element and the holding structure and which are designed so asto impose a pre-defined deformation into the optical element. Further, ameasuring device is provided which includes a reference structureconnected to the holding structure and at least one measuring unit, withthe at least one measuring unit being designed so as to detect ameasurement value representative of the geometry of the optical element,in particular a measurement value representative of a distance betweenthe reference structure and a measuring point of the optical element.The measuring device is designed so as to determine, using the firstmeasurement value, a detection value representative of a deformation ofthe optical element.

According to a further aspect, the present disclosure finally relates toa method for supporting an optical element, in particular formicrolithography, wherein the optical element is held, in particular ina statically determined manner, by a holding structure of a holdingdevice and a pre-defined deformation is imposed into the optical elementby a plurality of active deformation units of a deformation device ofthe holding device. By at least one measuring unit of a measuring deviceconnected to the holding structure, a measurement value representativeof the geometry of the optical element, in particular a measurementvalue representative of a distance between the reference structure and ameasuring point of the optical element, is detected, the measuringdevice determining, using the first measurement value, a detection valuerepresentative of a deformation of the optical element.

Further preferred embodiments of the disclosure will become evident fromthe dependent claims and from the following description of preferredembodiments, respectively, wherein reference is made to the attacheddrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a schematic illustration of a preferred embodiment of theoptical imaging device according to the disclosure, which includes anoptical device according to the disclosure and by which a preferredembodiment of a method according to the disclosure for supporting anoptical element can be carried out;

FIG. 2 shows a schematic sectional view of a preferred embodiment of theoptical device according to the disclosure of the optical imaging deviceof FIG. 1;

FIG. 3 shows a highly schematic top view of the optical device of FIG.2;

FIG. 4 shows a mechanical equivalent circuit diagram of the opticaldevice according to the disclosure;

FIG. 5 shows a block diagram of a preferred embodiment of the methodaccording to the disclosure for supporting an optical element, which canbe implemented using the optical device of FIG. 2;

FIG. 6 shows a schematic illustration of a part of a further preferredembodiment of the optical device according to the disclosure of theimaging device of FIG. 1;

FIG. 7 shows a schematic sectional view of a further preferredembodiment of the optical device according to the disclosure of theoptical imaging device of FIG. 1;

FIG. 8 shows a schematic sectional view of a further preferredembodiment of the optical device according to the disclosure of theoptical imaging device of FIG. 1;

FIG. 9 shows a schematic sectional view of a further preferredembodiment of the optical device according to the disclosure of theoptical imaging device of FIG. 1.

DETAILED DESCRIPTION OF THE DISCLOSURE First Embodiment

With reference to FIGS. 1 to 5, a preferred embodiment of the opticaldevice according to the disclosure will be described below, which isused in an optical imaging device according to the disclosure in thearea of microlithography.

FIG. 1 shows a schematic illustration of a preferred embodiment of theoptical imaging device according to the disclosure in the form of amicrolithography apparatus 101 that works with light in the UV rangewith a wavelength of 193 nm.

The microlithography apparatus 101 includes an illumination system 102,a mask device in the form of a mask table 103, an optical projectionsystem in the form of an objective 104 and a substrate device in theform of a wafer table 105. The illumination system 102 illuminates amask 103.1 placed on the mask table 103 via a projection light beam (notshown in more detail) having a wavelength of 193 nm. On the mask 103.1,a projection pattern is located which is projected via the projectionlight beam via the optical elements arranged in the objective 104 onto asubstrate in the form of a wafer 105.1 that is placed on the wafer table105.

Apart from a light source (not shown), the illumination system 102includes a group 106 of optically active components, which includes,amongst other things, a number of optical elements, for example theoptical element 106.1. Further, the objective 104 includes a furthergroup 107 of optically active components, which includes a number ofoptical elements, for example the optical element 107.1 which is shownin FIGS. 1 to 4 in a highly schematic form (as a plate with parallelfaces). In the present example with a working wavelength of 193 nm, theoptical elements 106.1, 107.1 are refractive optical elements. However,it will be understood that in other variants of the disclosure (inparticular with other working wavelengths), also refractive, reflectiveor diffractive optical elements (having optical surfaces of any desireddesign) may be used either alone or in arbitrary combinations.

The optically active components of the optical groups 106 and 107 definean optical axis 101.1 of the microlithography apparatus 101, which inthe present example is formed to be rectilinear. However, it will beunderstood that in other variants of the disclosure, the optical axismay also be chosen to have an arbitrarily kinked or folded course.

The optically active components of the group 107 are held in the housing104.1 of the objective 104 in appropriate optical devices. FIG. 2 showsa highly schematic illustration of an optical device 108 according tothe disclosure, which includes an optical module 109 and a supportstructure 110.

The support structure 110 is connected to the housing 104.1 of theobjective 104 and supports the optical module 109. To this end, thesupport structure 110 includes (optionally in addition to furthersupport elements) a number of support units 110.1 that are connected toa support ring 110.2 and to the optical module 109. The support ring110.2 is rigidly connected to the housing 104.1 of the objective 104 oris a component of the housing 104.1.

The optical module 109 includes a holding device 111 that holds theoptical element 107.1. To this end, the holding device 111 againincludes a holding structure in the form of a holding ring 111.1, onwhich a plurality of holding units 112 is supported. The holding units112 are connected to the optical element 107.1. In the present example,the holding units 112 engage directly on the optical element 107.1.However, it will be understood that in other variants of the disclosureit may also be provided that one or more further intermediate elementsare arranged between a part of the holding units and the opticalelement, for example a further (inner) holding ring, so that the forceflux between the optical element and the holding units concerned takesplace via the intermediate element concerned.

In the present example, one part of the holding units 112 is implementedas a positioning device having a plurality of positioning units 113,whilst the other part of the holding units 112 is implemented as adeformation device having a plurality of deformation units 114.

The positioning units 113 are designed in such a way (as will beexplained in more detail below) that they are primarily used foradjusting the position and/or the orientation of the optical element107.1 in space. The positioning units 113 may be (at least partially)passive components which are designed to be correspondingly adjustable,in order to adjust the position and/or the orientation of the opticalelement 107.1 (either once only or from time to time).

Preferably, the positioning units 113 are (at least partially) activecomponents which allow the position and/or the orientation of theoptical element 107.1 to be actively adjusted during the operation ofthe microlithography apparatus 101. For this purpose, the respectivepositioning unit 113 includes one or more active positioning elements113.1 (for example generally known actuators) which can be appropriatelycontrolled by a control device 115.

On the other hand, the deformation units 114 (as will be explained inmore detail below) are designed in such a way that they are primarilyused for adjusting the geometry of the optical element 107.1. In otherwords, the deformation units 114 are designed so as to specificallyimpose a pre-defined deformation on the optical element 107.1 in orderto correct at least partially any imaging errors of the optical element107.1 and/or of one or more other optical elements of themicrolithography apparatus 101, as this is known for example from US2003/0234918 A1 (Watson) which was mentioned in the beginning. For thispurpose, the deformation units 114 are connected to the control device114 that transmits corresponding control signals to the deformationunits 114. The control device 115 in turn determines these controlsignals using the detection signals from a detection unit 116 connectedto the control device 115. Via the detection unit 116, the current valueof one or more variables is determined in a manner generally known,which variable(s) is or are representative of the current value of therespective imaging error to be corrected.

By this approach it is possible to carry out, during the operation ofthe microlithography apparatus 101, via the active deformation of theoptical element 107.1, an (at least partially) active correction of oneor more imaging errors which occur during imaging of the projectionpattern of the mask 103.1 onto the substrate 105.1. In doing so, asufficiently high control bandwidth may be achieved, which does notintroduce any delays into the imaging process and therefore does nothave a negative effect on the throughput of the microlithographyapparatus 101.

As can be seen from FIG. 2, in the present example, three support units110.1 are provided in the area of three first supporting points, whichsupport units are evenly distributed over the circumference of theoptical module 109. In the present example, the support units 110.1 areeach designed in the style of a bipod, so that the support thus achievedof the optical module 109 is formed in the manner of a hexapod, viawhich a statically determined support of the optical module 109 (havinga certain natural frequency) is realised.

However, it will be understood that, in other variants of thedisclosure, any other desired support of the optical module may beselected. Preferably, however, this will as a rule be a staticallydetermined support in order to avoid as far as possible any undesireddeformation of the optical module.

In the present example, the optical module 109 is connected to thesupport units 110.1 of the support structure 110 in an easily detachableand thus replaceable manner via connecting units 117. In the presentexample, the easy replaceability is, amongst other things, ensured byvirtue of the fact that the connection between the optical module 109and the support units 110.1 can be released in a simple manner withoutaffecting the remaining structural integrity of the objective 104 or thefixed structural or spatial relationship existing after the assembly ofthe objective 104 between the remaining optical elements of the opticalgroup of elements 107.

This may be realised by the fact that, on the one hand, the connectingunits 117 are correspondingly easily accessible for releasing or laterre-establishing the connection and, on the other hand, the opticalmodule 109 can be taken out of the objective housing 104.1, withoutaffecting the spatial relationship between the other optical elements ofthe objective 104.

As a result it is possible to design the optical element 107.1 to becorrespondingly simple and lighter than in previous solutions with suchan active deformation. This is a result of the fact that both theoptical element 107.1 and the remaining components of the optical module109 do not need to be adapted to the lifetime of the objective 104and/or the microlithography apparatus 101. Rather, by virtue of the easyreplaceability it is possible to use components of a simpler and lighterdesign, which are easily replaced once they reach the end of theirlifetime.

These relaxed lifetime properties for the components of the opticalmodule 109 also make it possible to use for the positioning units 113and the deformation units 114, on the one hand, an element for theoptical element 107.1, the cross section of which is designed to becorrespondingly thin, and, on the other hand, components that aredesigned to be correspondingly light and thus smaller also.Consequently, the optical module 109 may be accommodated within acomparatively small space. Accordingly, it may now optionally even bepossible to realise such an active deformation in an existing design ofthe objective 104, which previously didn't provide for an activedeformation in the area of the optical element 107.1, without having tomodify the design of the optical imaging system (in particular thedistances between the optical elements of the element group 107 alongthe optical axis 101.1).

In the present example, the connecting units 117 are arranged at the endof the respective support unit 110.1, which faces the optical module109. However, it will be understood that in other variants of thedisclosure it may also be provided that the respective connecting unitis mounted in the central area of the associated support unit or on theend of the support unit, which faces away from the optical module. Thismeans in other words that it is also possible to replace at least partof the respective support unit together with the optical module.

As can be seen from FIG. 3, in the present example, three positioningunits 113 are provided which are evenly distributed over thecircumference of the optical element 107.1. In the present example, thepositioning units 113 are respectively designed in the manner of abipod, so that the positioning device thus formed is altogether formedin the manner of a hexapod, via which (in principle) a staticallydetermined support of the optical element 107.1 (having a certainnatural frequency) is realised.

The deformation units 114 are evenly distributed between the positioningunits 113 over the circumference of the optical element 107.1, so thatan altogether even distribution of the holding units 112 over thecircumference of the optical element 107.1 is achieved.

As can be seen from FIG. 2, the deformation units 114 are each formed byan actuator unit 114.1 supported on the holding ring 111.1 and by anelastic lever arm 114.2 as the transmission element. One end of theelastic lever arm 114.2 is rigidly fixed to the circumference of theoptical element 107.1, whilst the elastic lever arm 114.2 is connectedto the actuator unit 114.1 in the area of the other end thereof. Theactuation direction of the actuator unit 114.1 (i.e. the direction inwhich the actuator unit 114.1 develops its primary force effect F), in aneutral condition (without any force effect by the actuator unit 114.1),extends perpendicularly to the longitudinal axis of the lever arm 114.2.The force effect or motion transmission between the actuator unit 114.1and the point of action of the deformation unit 114 on the opticalelement 107.1 may be adjusted via the length L and the bending stiffnessof the lever arm 114.2.

FIG. 4 shows a mechanical equivalent circuit diagram of the opticalmodule 109, in which the various sections of the optical module 109 arerepresented by simplified equivalent components. Thus, the sectionbetween the respective i^(th) positioning element 118.1 and the opticalelement 107.1 is represented by a simple spring 118.1 of a firstrigidity C1 i, whilst the section between the positioning element 113.1and the support structure 110 is represented by a spring 118.2 of asecond rigidity C2 i. In this equivalent system, the support structure110 is assumed in good approximation as having an infinite rigidity.

A comparable approach is also chosen for the deformation units 114,wherein for the j^(th) deformation unit 114, the section between therespective actuator unit 114.1 and the optical element 107.1 isrepresented by a simple spring 118.3 of a third rigidity C3 j, whereasthe section between the actuator unit 114.1 and the support structure110 is represented by a spring 118.4 of a fourth rigidity C4 j.

It is to be noted at this point that the rigidities C1 i to C4 j arerespectively equivalent rigidities for the rigidities in the directionof the (main) load (i.e. a force and/or a momentum) present (uponactuation) on the respective component. These equivalent rigidities maytherefore be the calculated rigidity of the transmission element 114.2which results at the location of the actuator unit 114.1 in theactuation direction F, or the calculated rigidity of the holding ring111.1 related to the location of the actuator unit 114.1.

In other words, the respective equivalent rigidity is a (calculated)rigidity that is related to the location of the actuator unit 114.1 orof the positioning element 113.1, which is determined at the location ofthe actuator unit 114.1 or of the positioning element 113.1 (in theacting direction of the actuator unit 114.1 or of the positioningelement 113.1) from the active load (of the actuator unit 114.1 or ofthe positioning element 113.1) and from that displacement that isobtained:

-   -   (i) at the location of the actuator unit 114.1 or of the        positioning element 113.1,    -   (ii) under the active load acting at the location of the        actuator unit 114.1 or of the positioning element 113.1;    -   (iii) from the deformation (effected by the active load) of the        respective component (for which the reference rigidity was        determined).

In the present example, the i (=3) positioning units 113 are formed tobe as rigid as possible in the direction of the force flux (that actstherein as they support the optical element 107.1), i.e. the respectivefirst and second rigidities C1 i and C2 i are chosen to be as high aspossible so as to achieve the position and the orientation of theoptical element 107.1 to be established with a predeterminable highnatural frequency. The actual rigidity of the component is thereforedetermined by the desired natural frequency of the support. To this end,on the one hand, the respective connection between the positioningelement 113.1 and the optical element 107.1 is implemented to becorrespondingly rigid. Further, on the other hand, the connectionbetween the positioning element 113.1 and the holding ring 111.1 isimplemented to be correspondingly rigid. Finally, the support by theholding ring 111.1 itself is implemented to be as rigid as possible inthis area.

In order to keep the effort for stiffening the holding ring 111.1 as lowas possible, it is provided in the present example that the respectivepositioning unit 113 is positioned at a second supporting point which inturn is located in the area of the first supporting point, where theoptical module 109 is supported on the support structure, so that theeffect of the rigidity of the holding ring 111.1 on the rigidity of thesupport of the optical module 109 is kept low.

The rigidity of the holding ring 111.1 in the area of the secondsupporting point, which is related to the location of the positioningelement 113.1, corresponds in the present example to at least therigidity of the positioning element 113.1 in the acting directionthereof.

However, it will be understood that, in other variants of thedisclosure, it may also be provided that the rigidity of the holdingring 111.1, which is related to the location of the positioning element113.1, corresponds to at least 5% to 10% of the rigidity of thepositioning element 113.1 in the acting direction thereof. Thus, thepositioning element 113.1 may also be more rigid than the holding ring111.1. In particular, the rigidity of the positioning element 113.1 maysignificantly exceed the rigidity of the holding ring 111.1, which isrelated to the location of the positioning element 113.1 (it mayoptionally even amount to ten to twenty times the rigidity of theholding ring 111.1, which is related to the location of the positioningelement 113.1).

However, it will be understood that, in further variants of thedisclosure, it may also be provided that the rigidity of the holdingring 111.1, which is related to the location of the positioning element113.1, is greater than the rigidity of the positioning element 113.1. Inthese cases, the rigidity of the holding ring 111.1, which is related tothe location of the positioning element 113.1, preferably amounts to upto 150%, preferably to up to 200% of the rigidity of the positioningelement 113.1 in the acting direction thereof. Thus, the holding ring111.1 may also be more rigid than the positioning element 113.1.

In the present example, the respective positioning element 113.1 itselfalso has a high rigidity in its acting direction (and thus in thedirection of the force flux), and this may be any desired suitableactuator that has appropriate mechanical properties and has a sufficientadjustment range.

By contrast, in the present example the j (=9) deformation units 114 areimplemented to be as soft as possible (i.e. at least one of therespective third and fourth rigidities C3 j and C4 j is selected to besignificantly lower especially by comparison with the first and secondrigidities C1 i and C2 i) in the direction of the load flow (which actstherein as they support the optical element 107.1) (i.e. the force fluxand/or the momentum flux), in order to achieve an impact as small aspossible of the shape function FDj from rigidities other than that ofthe optical element 107.1 for the respective deformation unit 114.

The shape function FDj identifies, in terms of the present disclosure,the deformation response of the optical element 114 to a pre-defined(normalised) displacement and/or a pre-defined (normalised) load effect(force effect and/or momentum effect) in the area of the actuator unit114.1, optionally after subtraction of the rigid body movements of theoptical element 107.1, which may be adjusted by the three positioningelements 113.1. If the shape function is only dependent on the rigidityof the optical element 107.1, it may be determined in advance for eachactuator position in a simple manner (e.g. analytically).

Depending on the design of the deformation units 114, these loads may bea pure momentum, a pure force or a combination of force and momentum. Ifin the present example a linearly acting actuator is used for theactuator unit 114.1, both a momentum (about an axis extendingtangentially relative to the circumferential direction of the opticalelement 107.1) and a force (substantially parallel to the optical axis101.1) is introduced into the optical element via the elastic lever arm114.2. However, it will be understood that in other variants of thedisclosure it may be provided, amongst other things, that the actuatorunit only introduces a momentum into the lever arm and thus into theoptical element.

In the case of the above-described simple determination of the shapefunction FDj between the individual deformation units 114 it isadvantageously possible to adjust, in sufficiently good approximation, apre-defined deformation of the optical element 107.1 via a simplecontrol without a complex control algorithm, provided the shape functionFDj is known. The shape function FDj may here have been determined inadvance theoretically (for example appropriate simulation calculations)and/or experimentally (for example by appropriate measurements) and mayhave been deposited in the control device 115 as a corresponding model.

Preferably, the third rigidity C3 j is selected to be particularly smallcompared to the fourth rigidity C4 j, in order to keep any disturbanceof the shape functions FDj by the rigidities C4 j in the individualdeformation units 114 low. In this case, the desired properties withregard to the fourth rigidity C4 j, in particular the amount of rigidityof the holding ring 111.1 that is introduced therein, are low. Thus, inthis case the holding ring 111.1 does not need to be implemented to beparticularly rigid, which has a positive effect on the installationspace desired for the optical module 109.

Preferably, the ratio between the third rigidity C3 j and the fourthrigidity C4 j is selected such that (in the respective load direction)the fourth rigidity C4 j amounts to at least 500 times, preferably atleast 100 times the fourth rigidity C3 j. As a result, a particularlyfavourable, low disturbance of the shape function FDj may be achieved.

In a case with a third rigidity C3 j that is small compared to thefourth rigidity C4 j, a simple displacement actuator may be used for theactuator unit 114.1, which generates a pre-defined displacement in itsacting direction as a function of a pre-defined control signal. By this,a control of a particularly simple design may be realised, since by suchdisplacement actuators, the specification (and checking) of apre-defined travel range can as a rule be carried out in a very simplemanner. Depending on the type of actuator used, for example, only asimple specification and/or counting of the revolutions of the actuatoror the like is involved.

With respect to the rigidity of the actuator unit 114.1 it is to benoted that the third rigidity C3 j, i.e. the rigidity of the elasticlever arm 114.2 (as the transmission element between the actuator unit114.1 and the optical element 107.1), which is related to the locationof the respective actuator unit 114.1, is preferably significantlysmaller in the actuation direction of the respective actuator unit 114.1than the rigidity of the actuator unit 114.1 in its actuation direction.Preferably, the rigidity of the elastic lever arm 114.2, which isrelated to the location of the actuator unit 114.1, amounts to no morethan 0.1% of the rigidity of the actuator unit 114.1 in the actuationdirection thereof.

The actuator unit 114.1 in turn is preferably a unit that has (similarto the positioning element 113.1) a comparatively high rigidity in itsacting or actuation direction. In particular, the rigidity of theactuator unit 114.1 and the rigidity of the holding ring 111.1 may inturn be matched to each other in such a way that, in the presentexample, the rigidity of the holding ring 111.1 (in the area of thepoint of action of the respective deformation unit 114), which isrelated to the location of the actuator unit 114.1, approximatelycorresponds to the rigidity of the actuator unit 114.1 in the actingdirection thereof.

However, it will be understood that, in other variants of thedisclosure, it may also be provided that the rigidity of the holdingring 111.1, which is related to the location of the actuator unit 114.1,corresponds to at least 5% to 10% of the rigidity of the positioningelement 113.1 in the acting direction thereof. Thus, the actuator unit114.1 may also be more rigid than the holding ring 111.1. In particular,the rigidity of the actuator unit 114.1 may significantly exceed therigidity of the holding ring 111.1 (it may optionally even amount to tento twenty times the rigidity of the holding ring 111.1), which isrelated to the location of the actuator unit 114.1.

However, it will be understood that, in further variants of thedisclosure, it may also be provided that the rigidity of the holdingring 111.1, which is related to the location of the actuator unit 114.1,may also be greater than the rigidity of the actuator unit 114.1. Inthese cases, the rigidity of the holding ring 111.1, which is related tothe location of the actuator unit 114.1, preferably amounts to up to150%, preferably to up to 200%, of the rigidity of the actuator unit114.1 in the acting direction thereof. Thus, the holding ring 111.1 mayalso be more rigid than the actuator unit 114.1.

In other variants of the disclosure, the actuator unit 114.1 may also bea force actuator that generates a pre-defined force in the actingdirection thereof as a function of a pre-defined control signal. In thiscase there is the advantage that the rigidity of the support of theactuator unit 114.1 on the side of the support structure and/or thedesign of the holding ring 111.1 is almost free, because it has nosignificant influence on the shape function FDj by virtue of thepre-defined force effect of the actuator unit 114.1.

In both cases it will always be of advantage if the variance of thethird rigidity C3 j is as low as possible so as to achieve an altogetherminor disturbance of the shape functions FDj.

In the present example, the effect of a deformation of the holding ring111.1, which is due to the actuation of the deformation units 114, onthe position and/or the orientation of the optical element 107.1 isreduced. However, it will be understood that in other variants of thedisclosure, where no such arrangement of the positioning units in theimmediate vicinity of the support units exists, a simple correction of amodification of the position and/or the orientation of the opticalelement, which results from the active deformation, can be achieved viathe positioning units 113.

In the present example, the support units 110.1 are designed as activeunits, via which the position and/or the orientation of the opticalmodule 109 can be modified. To this end, the support units 110.1 are inany case connected to the control device 115 by which they are, ifdesired, appropriately controlled. For the support units 110.1, anydesired suitable actuators may be used that enable a correspondingactive adjustment to be carried out.

Herewith it is possible, amongst other things, to realise coarser orgreater modifications of the position and/or the orientation of theoptical module 109 and thus of the optical element 107.1, as areinvolved for example for rapid changes of the so-called setting of theoptical imaging system, whilst the fine adjustment of the positionand/or orientation of the optical element 107.1 is carried out via thepositioning units 113 and the fine adjustment of the geometry of theoptical element 107.1 is carried out via the deformation units 114.

By this approach it is further possible to move the optical module 109optionally into a replacement position (which is different from anoperating position during the exposure of the substrate 105.1), in whichthe connecting units 117 may be released in a simple manner and theoptical module 109 may be removed from the objective 104 in a simplemanner.

However, it will be understood that in other variants of the disclosure,the support units may also be formed at least partially as passiveelements. Here, of course, also a manual adjustability for the supportunits may be provided.

In the present example, an adjustment of the position/orientation of theoptical element 107.1 and, in particular, a correction of the imagingerrors of the imaging system may be realised via an active deformationof the optical element 107.1 in the following way during the operationof the microlithography device 101.

FIG. 5 shows a flow chart of an imaging process that is carried outusing the microlithography apparatus 101 and wherein a preferredembodiment of the method according to the disclosure for supporting anoptical element is applied.

Initially, the process is started in a step 119.1. In a step 119.2, thecomponents of the microlithography apparatus 101 of FIG. 1 are thenmoved into a condition in which the above-described imaging of theprojection pattern of the mask 103.1 onto the substrate 105.1 may becarried out.

In an imaging step 119.3, the above-described detection of the currentvalue of the at least one variable representative of an imaging error ofthe optical imaging system is carried out at the same time as theexposure of the substrate 105.1 in a step 119.4 via the detection device116 and the forwarding of the detected value of this variable to thecontrol device 115.

In this step 119.4, the currently detected value of this variable isthen compared in the control device 115 with a predetermined setpointvalue for this variable for the current operating condition of themicrolithography apparatus 101. From this comparison, the control device115 determines, on the one hand, a specification for the geometry of theoptical element 107.1, i.e. a specification for the deformation of theoptical element 107.1, and determines therefrom, on the one hand,control signals for the actuator units 114.1 of the deformation units114.

Moreover, the control device 115 determines from this comparison aspecification for the position and/or the orientation of the opticalelement 107.1 and determines therefrom control signals for thepositioning elements 113.1 of the positioning units 113. Optionallyhere, a modification to be expected of the position and/or theorientation of the optical element 107.1, which results from the forceeffect of the deformation units 114 which is to be adjusted, will betaken into account. To this end, the control device 115 can access astored model (which was previously determined theoretically and/orexperimentally) of the optical module 109, which represents themodification to be expected of the position and/or the orientation ofthe optical element 107.1 as a function of the force effect of thepositioning element 113.1.

Optionally, the control device 115 determines from the aforementionedcomparison and/or on the basis of another specification from the imagingprocess to be carried out also a specification for the position and/orthe orientation of the optical module 109 and thus also of the opticalelement 107.1 and determines therefrom control signals for the supportunits 110.1.

In a step 119.5, the control device 115 then, in the manner describedabove, controls the actuator units 114.1 of the deformation units 114,the positioning elements 113.1 of the positioning units 113 andoptionally the support units 110.1 using the determined control signals,in order to counteract any deviation of the current condition of theoptical module 109, in particular of the optical element 107.1, from asetpoint condition that was specified for the present operatingcondition, in particular to counteract a currently present imagingerror.

Here, the low rigidity of deformation units 114 in the load directionhas the advantage that a correction of the position and/or theorientation of the optical element 107.1 via the positioning units 113only entails a comparatively minor, as a rule negligible modification ofthe geometry of the optical element 107.1, which is adjusted via thedeformation units 114, so that a corresponding control loop whichdetects the actual geometry of the optical element 107.1 may bedispensed with.

Subsequently, it will be checked in a step 119.6, whether a furtherimaging step has to be carried out. If this is not the case, the processwill be terminated in step 119.7. Otherwise, the process goes back tostep 119.3.

In the present example, the optical element 107.1 is supported on theholding ring 111.1 by the positioning units 113 and the deformationunits 114. However, it will be understood that in other variants of thedisclosure, a further support of the optical element on the holding ringmay be provided. This further support may be, for example, implementedin the style of a generally known gravity compensation device, as isschematically indicated in FIG. 2 by the dotted line 120. This gravitycompensation device 120 may be a multiplicity of soft spring elementsthat are evenly distributed over the circumference of the opticalelement 107.1. The gravity compensation device 120 may be implemented asa passive and/or an active device and may accommodate in a conventionalmanner at least a large part of the weight force of the optical element107.1.

Moreover, in the present example, the support of the optical element107.1 is shown as a standing support (i.e. the holding ring 111.1supports the optical element 107.1 from below). However, it will beunderstood that the support of the optical element may also beimplemented as a suspended support, which means the optical element issuspended from the holding ring (from below). However, it will furtherbe understood that in other variants of the disclosure, also any otherdesired orientation of the optical element relative to the verticaldirection may be provided.

Second Embodiment

A further preferred embodiment of the optical device 208 according tothe disclosure will be described below with reference to FIGS. 1 to 5and 6, which may be used in the objective 104 instead of the opticaldevice 108. The optical device 208, in its structure and functionality,in principle corresponds to the optical device 108, so that only thedifferences will be addressed here. In particular, identical or likecomponents are identified here with reference numerals that arerespectively increased by 100. Unless otherwise stated below, in termsof the properties and functions of these components, reference is madeto the above explanations given with regard to the first embodiment.

The optical device 208 differs from the optical device 108 only inrespect of the design and the connections of the deformation units 214to the optical element 207.1. FIG. 6 shows a detail of the opticaldevice 208 which, in terms of its position, corresponds to detail VI inFIG. 2.

As can be seen from highly schematic FIG. 6, in this embodiment, thetransmission element 214.2 of the deformation unit 214 is formed as alever arm that is connected (between its two ends) to the holding ring211.1 in an articulated manner. The articulated support on the holdingring 211.1 may be designed in any desired way. It is preferably formedin the style of a solid-body joint.

The lever arm 214.2 in turn is connected with one end to an actuatorunit 214.1, whilst the other end is of a fork-shaped design and actsfrom both sides (which approach, in the present horizontal installationposition of the optical element 207.1 from the top and from the bottom)on a projection 207.2 on the circumference of the optical element 207.1respectively via an elastic section 214.3 and 214.4. The above-describedlow rigidity of the transmission element 214.2 can in this design beachieved and adjusted through the rigidity of the lever arm 214.2 and/orthe rigidity of the elastic sections 214.3 and 214.4.

The present design has the advantage that it may be applied in a simplemanner with conventional designs for optical elements, which oftenalready have one (continuous) or more (usually evenly distributed) suchprojections 207.2 on the circumference thereof. Particularlyadvantageously therefore, the present solution may thus be incorporatedinto a design that is principally known, wherein the optical element207.1 is supported in a generally known manner (optionally in additionto further support devices) via a gravity compensation device, whichincludes a multiplicity of spring elements which are distributed overthe circumference of the optical element 207.1 and which engage on aflange 207.2 of the optical element 207.1, as is indicated in FIG. 6 bythe dotted contour 220.

However, it is to be understood that, in other variants of thedisclosure, also any other desired design of the transmission elementmay be chosen. It is in particular possible, as will be explained indetail below, to design also the transmission element itself as well asits connection with the optical element to be especially rigid, in orderto impose a predetermined deformation directly on the optical element.

Third Embodiment

A further preferred embodiment of the optical device 308 according tothe disclosure will be described below with reference to FIGS. 1, 4, 5and 7, which may be used instead of the optical device 108 in themicrolithography apparatus 101 and by which the method of FIG. 5 may becarried out. The optical device 308, in its structure and functionality,in principle corresponds to the optical device 108 of FIG. 2 (whereinthe mechanical equivalent circuit diagram from FIG. 4 may also be usedfor the optical device 308), so that only the differences will beaddressed here. In particular, identical or like components areidentified here with reference numerals that are respectively increasedby 200. Unless otherwise stated below, in terms of the properties andfunctions of these components, reference is made to the aboveexplanations given with regard to the first embodiment.

The difference between the optical device 308 and the optical device 108lies in the design of the holding units 312. Whilst here again a numberof deformation units 314 which are evenly distributed over thecircumference of the optical element 307.1 are provided, in thisvariant, a gravity compensation device 320 is provided instead of thepositioning units 113. This gravity compensation device 320 includes amultiplicity of spring elements 320.1 evenly distributed over thecircumference of the optical element 307.1, which accommodate in agenerally known manner the weight force of the optical element 307.1.However, the spring elements 320.1 are formed here to be comparativelyrigid (i.e. the first rigidity C1 i in FIG. 4 is by a factor ofapproximately 500 to 1,000 higher than C3 j).

Each of the deformation units 314 includes an actuator unit 314.1 whichis also comparatively rigid (in its actuation direction) and whichprovides for short travel ranges with a high resolution. To this end,principally any desired actuators may be used which fulfil this desiredproperty. For example, piezo actuators, mechanical linear drives whereina vertical movement is generated by a rotational drive via acorresponding transmission or the like may be used for this purpose. Theadvantages of such actuators include the fact that they may beimplemented to be particularly compact.

Further, in the present example the j deformation units 314 areimplemented to be as rigid as possible (i.e. the third rigidity C3 j iscomparatively high) in the force flux direction (which acts therein asthey support the optical element 307.1), in order to realise apredeterminable high natural frequency of the support. This may berealised, for example, in the area of the transmission element 314.2 byforming the same as a correspondingly rigid radial extension of theoptical element. For example, this may simply be a lever arm 314.2 thatis monolithically formed at the optical element 307.1. The rigidities C2j and C4 j according to FIG. 4, both of which represent here therigidity of the holding ring 311.1 at the location j, will be addressedbelow.

With the design described above, a comparatively large number ofinfluencing parameters on the shape functions FDj of the respectivedeformation units 314 may eventually result. Thus, the respectiveactuator unit 314.1 generates, with the same travel range or the samedisplacement V, another shape function FDj as well as other rigid bodymovements. These are dependent on the position of the respectivedeformation unit 314 (in the circumferential direction of the opticalelement 307.1) and the respective values of the first and thirdrigidities C1 j, C3 j and the fourth rigidity C4 j.

As mentioned before, in terms of the present disclosure, the shapefunction FDj indicates the deformation response of the deformation unit314 to a pre-defined (normalised) displacement and/or a pre-defined(normalised) force effect in the area of the actuator unit 314.1. Thus,the shape function FDj is also representative of the loads that areintroduced into the optical element 307.1 with the pre-defineddisplacement and/or force effect.

In view of the above-described comparatively large variation of theshape function FDj between the individual deformation units 314 it is ofadvantage if the fourth rigidity C4 j is as high as possible, whichmeans in particular that also the holding ring 311.1 is formed to beparticularly rigid, in order to keep the effect of any deformations ofthe holding ring 311.1, which result from the actuation of one of thedeformation units 314, on the position and/or the orientation of theother deformation units 314 as low as possible.

In a borderline case for a holding ring 311.1 designed to be infinitelyrigid with rigidities C1 j, C3 j that are identical with each other, thesame shape function would then be obtained for each actuator unit, ifthe actuator units were equidistantly arranged on the samecircumference.

In this case it would then advantageously be possible to adjust—insufficiently good approximation—a pre-defined deformation of the opticalelement 307.1 via a simple control without a complex control algorithm,provided the respective shape function FDj is known. The shape functionFDj may have been determined theoretically (for example by appropriatesimulation calculations) and/or experimentally (for example byappropriate measurement) in advance and stored in the control device 315as a corresponding model.

In the control device 315, the currently detected value of the variablerepresentative of the imaging error to be corrected is then compared instep 119.4 of FIG. 5 with a setpoint value for this variable, which wasspecified for the current operating condition of the microlithographyapparatus 101. From this comparison, the control device 315 thendetermines (for example by way of an appropriate adaptation using thestored functions FDj) a specification for the geometry of the opticalelement 307.1, which means a specification for the deformation of theoptical element 307.1 as well as a specification for the position andthe orientation of the optical element 307.1, and determines from thisthe control signals for the actuator units 314.1 of the deformationunits 314, via which the deformation, the position and the orientationof the optical element 307.1 will be adjusted. For this purpose, thecontrol device 315 accesses the stored model (which was previouslytheoretically and/or experimentally determined) of the optical module309.

Optionally, the control device 315 additionally determines from theabove-mentioned comparison and/or by a different specification from theimaging process to be carried out a further specification for theposition and/or the orientation of the optical module 309 and thus alsoof the optical element 307.1, and determines from this further controlsignals for the support units 310.1.

In step 119.5, the control device 315 then controls in theabove-described manner the actuator units 314.1 of the deformation units314 and optionally the support units 310.1 by the determined controlsignals, in order to counteract any deviation of the current conditionof the optical module 309, in particular of the optical element 307.1,from a setpoint condition specified for the present operating condition,in particular to counteract a currently present imaging error.

The above-described design has the advantage that it may be designed, inparticular with respect to the actuators, to be especially compact andthat it is therefore particularly suitable for the integration of anactive deformation of an optical element into a pre-existing opticaldesign. Optionally, it is also possible with this variant to replace, inan existing design of an optical imaging system, one of the previousoptical elements with the optical element 307.1 that is disposed in theoptical module 309, without having to modify the remaining design of theoptical imaging system.

In this case, the support units 310.1 are again advantageouslydetachably connected to the optical module 309 so as to ensure that theoptical module 309 can be replaced in a simple manner. However, it willbe understood that, in other variants of the disclosure, such aconnection between the optical module and the support structure, whichcan be released in a simple manner, may also be absent.

In the present example, again a simple displacement actuator may be usedfor the actuator unit 314.1, which displacement actuator generates apre-defined displacement in its acting direction as a function of apre-defined control signal. In other variants of the disclosure, theactuator unit 314.1 may again be a force actuator that generates apre-defined force in its acting direction as a function of a pre-definedcontrol signal. In any case it is of advantage in both cases if thevariance of the third rigidity C3 j is as low as possible, in order toachieve an altogether low variance of the shape function FDj.

In the present example, the support of the optical element 307.1 isfurther shown as a suspended support (i.e. the optical element 107.1 issuspended to the holding ring 311.1 from below). However, it will beunderstood that the support of the optical element may also be designedas a standing support, which means that the optical element is supportedon the holding ring (from above). To this end, in particular, forexample a configuration similar to the arrangement shown in FIG. 6 maybe selected. It will further be understood that in other variants of thedisclosure, of course, also any other orientation of the optical elementin relation to the vertical direction may be contemplated.

Fourth Embodiment

A further preferred embodiment of the optical device 408 according tothe disclosure will be described below with reference to FIGS. 1, 4, 5and 8, which may be used instead of the optical device 108 in themicrolithography apparatus 101 and by which the method of FIG. 5 may becarried out. The optical device 408, in its structure and functionality,in principle corresponds to the optical device 308 of FIG. 7 (whereinthe mechanical equivalent circuit diagram from FIG. 4 may also be usedfor the optical device 408), so that only the differences will beaddressed here. In particular, identical or like components areidentified here with reference numerals that are respectively increasedby 100. Unless otherwise stated below, in terms of the properties andfunctions of these components, reference is made to the aboveexplanations given with regard to the third and first embodiment,respectively.

The difference between the optical device 408 and the optical device 308lies in the design of the holding units 412. In the present example,these include exclusively a number of deformation units 414 which areevenly distributed over the circumference of the optical element 407.1.Each of the deformation units 414 in turn includes an actuator unit414.1 which is comparatively rigid (in its actuation direction) andwhich provides small travel ranges with a high resolution. For thispurpose, in principle any desired actuators may be used which fulfilthis desired property. For example, piezo actuators, mechanical lineardrives in which a vertical movement is generated by a rotational drivevia a corresponding transmission or the like may be used for thispurpose. The advantages of such actuators include the fact that they maybe designed to be especially compact.

In the present example, the j deformation units 414 are again formed tobe as rigid as possible (i.e. the third rigidity C3 j and the fourthrigidity C4 j are also comparatively high) in the force flux direction(which acts therein as they support the optical element 407.1) so as torealise a predeterminable high natural frequency of the support.

With the above-described design, optionally a comparatively highvariance of the shape functions FDj of the respective deformation units414 is again achieved. This means, the respective actuator unit 414.1generates, with the same travel range and the same displacement V, adifferent shape function FDj as well as different rigid body movements.These are dependent on the position of the respective deformation unit414 (in the circumferential direction of the optical element 407.1) andthe respective value of the third rigidity C3 j and the fourth rigidityC4 j.

As has already been mentioned, in terms of the present disclosure, theshape function FDj indicates the deformation response of the deformationunit 414 to a pre-defined (normalised) displacement and/or a pre-defined(normalised) force effect in the area of the actuator unit 414.1.Therefore, the shape function FDj is also representative of the loadsthat are introduced into the optical element 407.1 during thepre-defined displacement and/or force effect.

In order to keep the complexity of the design of the deformation units414 and the holding ring 411.1 low so as to reduce the disturbance ofthe shape functions FDj, a measuring device 421 is provided in thepresent example, which includes an annular reference structure 421.1 anda plurality of measuring units 421.2, which are distributed (preferablyevenly) over the circumference of the reference structure 421.1.

The respective measuring unit 421.2 detects in any desired suitablemanner a measurement value (with sufficient accuracy), the measurementvalue that is representative of the geometry of the optical element407.1. In the present example, a measurement value is detected for thispurpose, which is representative of the distance between a referencepoint on the reference structure 421.1 (for example a point in the areaof the connection of the respective measuring unit 421.2 with thereference structure 421.1) and an associated measuring point on theoptical element 407.1. To this end, any suitable measurement principles(interferometric principles, capacitive principle, fibre-opticalsensors, scales etc.) that allow a sufficiently precise detection of thedistance may be used either individually or in combination. However, itwill be understood that in other variants of the disclosure, also anyother measurement principles may be applied instead of or in addition tosuch a distance measurement, which allow a conclusion to be made as tothe current geometry of the optical element.

From the values of the respective measuring variables, which wereobtained in this way using the individual measuring units 421.2, one ormore detection values may be determined, which allow conclusions to bemade as to the current geometry and thus the current deformation of theoptical element 407.1. In the present example, the use of the distancemeasurement here has the further advantage that in addition conclusionsmay be made as to the position and/or the orientation of the opticalelement 407.1.

In the control device 415, the currently detected value for the variablerepresentative of the imaging error is then compared with a setpointvalue for this variable in step 119.4 of

FIG. 5, which is specified for the current operating condition of themicrolithography apparatus 101. From this comparison, the control device415 determines (for example by an appropriate adaptation using thestored functions FDj) a specification for the geometry of the opticalelement 407.1, which means a specification for the deformation of theoptical element 407.1, and determines therefrom the control signals forthe actuator units 414.1 of the deformation units 414, via which thedeformation, the position and the orientation of the optical element407.1 will be adjusted. To this end, the control device 415 accesses, ifdesired, a stored model (which was theoretically and/or experimentallydetermined) of the optical module 409. Further, it optionally takes intoaccount here the detection value(s) determined in the above-describedmanner, which is or are representative of the current deformation,position and/or orientation of the optical element 407.1.

If desired, the control device 415 additionally determines from theaforementioned comparison and/or from another specification from theimaging process to be carried out a further specification for theposition and/or the orientation of the optical module 409 and thus alsoof the optical element 407.1 and optionally determines from this furthercontrol signals for the support units 410.1.

In step 119.5, the control device 415 then controls in theabove-described manner the actuator units 414.1 of the deformation units414 and optionally the support units 410.1 using the determined controlsignals, in order to counteract any deviation of the current conditionof the optical module 409, in particular of the optical element 407.1,from a setpoint condition specified for the present operating condition,in particular to counteract a currently present imaging error. In thisconnection, the current condition (the deformation, the position and/orthe orientation in relation to the reference structure 421.1) of theoptical element 407.1 is continuously detected via the measuring unit421 and is processed in the control device 214 so as to achieve that thecurrent preset condition is quickly reached via a control loop realisedin this way.

The above-described design including the measuring device 421 has theadvantage that, apart from the achievement of a certain predeterminednatural frequency, no particular further desired properties will have tobe met by the support of the optical element 407.1 in relation torigidity (in particular of the holding units 412 and the holding ring411.1), so that there is a greater freedom of design in this respect. Inparticular, any desired suitable actuators as well as any desiredsuitable transmission elements may be used here. Preferably, however, arigidity as high as possible is provided here in particular for thedeformation units 414 and the holding ring 411.11.

Due to the freedom of design obtained in this way it is possible todesign the components of the optical module 409 in a space optimisedmanner, so that this solution is also particularly well suited for theintegration of an active deformation of an optical element in apre-existing optical design. If desired, it is therefore possible withthis variant to replace in an existing design of an optical imagingsystem one of the previous optical elements with the optical element407.1 disposed in the optical module 409, without having to modify theremaining design of the optical imaging system.

In this case, the support units 410.1 are again advantageouslydetachably connected to the optical module 409, in order to ensure thatthe optical module 409 may be replaced in a simple manner. However, itwill be understood that, in other variants of the disclosure, such aconnection between the optical module and the support structure, whichcan be released in a simple manner, may also be absent.

In the present example, a simple displacement actuator may again be usedfor the actuator unit 414.1, which generates a pre-defined displacementin its acting direction as a function of a pre-defined control signal.In other variants of the disclosure, the actuator unit 414.1 may againbe a force actuator that generates a pre-defined force in its actingdirection as a function of a pre-defined control signal.

With regard to the design of the reference structure 421.1 it is to benoted that the latter preferably has a sensitivity with regard tothermal and/or mechanical disturbances, which is as low as possible.Preferably, it is therefore realised from one or more materials having alow thermal expansion coefficient and a high rigidity. Examples of suchmaterials include SiO₂, glass ceramics, Invar® etc.

It is to be noted at this point for the sake of completeness that such amaterial selection may also be of advantage for the remaining componentsof the respective optical module and the respective support structure ofall of the embodiments of the present disclosure. In the presentexample, the reference structure 421.1 is supported on the holding ring411.1. However, it will be understood that, in other variants of thedisclosure, it may also be provided that the reference structure issupported on the support structure 410.2. In the present example, thesupport of the reference structure 421.1 is preferably designed in sucha way that a deformation of the holding ring 411.1 has, if possible, noeffect on the position and/or the orientation of the reference structure421.1. In the present example this is realised by the fact that thereference structure is supported on the holding ring 411.1 in the areaof three supporting points, statically determined, which are arranged inthe area of the three supporting points on which the holding ring 411.1is supported by the support units 410.1.

Fifth Embodiment

A further preferred embodiment of the optical device 508 according tothe disclosure will be described below with reference to FIGS. 1, 4, 5and 9, which may be used instead of the optical device 108 in themicrolithography apparatus 101 and on which the method of FIG. 5 may becarried out. The optical device 508, in its structure and functionality,in principle corresponds to the optical device 108 of FIG. 2 (whereinthe mechanical equivalent circuit diagram from FIG. 4 may also be usedfor the optical device 508), so that only the differences will beaddressed here. In particular, identical or like components areidentified here with reference numerals that are respectively increasedby 400. Unless otherwise stated below, in terms of the properties andfunctions of these components, reference is made to the aboveexplanations given with regard to the first embodiment.

The only difference between the optical device 508 and the opticaldevice 108 is that the deformation units 514 (which are otherwiseconstructed in a manner identical with the deformation units 114) arenot directly supported on the holding ring 511.1 but on a separate (fromthe holding ring 511.1) abutment structure in the form of an abutmentring 522. This abutment ring 522 is in turn supported (preferably in astatically determined way) on the holding ring 511.1 (in the presentexample suspended), on which the optical element 507.1 is supported viapositioning units 513 (which are designed to be identical with thepositioning units 113). Otherwise, the optical module 509 is identicalwith the optical module 109.

In the present example, the support of the abutment ring 522 ispreferably designed in such a way that a deformation of the holding ring511.1 has an effect on the position and/or the orientation of theabutment ring 522 that is as low as possible. In the present examplethis is realised by the fact that the abutment ring 522 is supported, ina statically determined way, on the holding ring 511.1 in the area ofthree supporting points which are arranged in the area of the threesupporting points, on which the holding ring 511.1 is supported on thesupport structure 510.2 by the support units 510.1.

By this abutment structure that is separate from the holding structureit is, for example, possible to provide in a simple manner apre-existing optical module or a pre-existing design of such an opticalmodule with an active deformation of the optical element. It is to beunderstood in this connection that such a separate abutment structuremay be introduced not only in the case of a design as described inconnection with the first embodiment, but that it can be used also forany other designs, in particular the designs from the other embodiments.

As was indicated in FIG. 9 by the dotted contour 521, in other variantsof the disclosure, it is provided that a measuring device (which is, forexample, identical in terms of its structure and functionality with themeasuring device 421) is also supported on the separate abutmentstructure 522.

The present disclosure was described above by examples, in whichexclusively optically active elements of an objective were activelydeformed. However, it is to be noted again at this point that thedisclosure may of course also be used for the active deformation ofother optically active elements, for example of optical elements of theillumination device or of other optically active components of theimaging device, in particular of components of the mask device and/or ofthe substrate device.

Finally, it is to be noted that the present disclosure was describedabove examples from the field of microlithography. However, it is to beunderstood that the present disclosure may also be used for any otherapplications or imaging processes, in particular with any desiredwavelengths of the light used for imaging.

1.-20. (canceled)
 21. An optical device, comprising: an optical modulecomprising an optical element and a holding device that holds theoptical element; and a support structure supporting the optical module,wherein: the holding device comprises a deformation device comprising aplurality of active deformation units contacting the optical element;the plurality of active deformation units are configured to impose apre-defined deformation on the optical element; and the optical modulereplaceable manner.
 22. The optical device of claim 21, wherein: theholding device includes a holding structure supporting the opticalelement; and the holding structure is detachably connected to thesupport structure in an area of a first supporting point.
 23. Theoptical device of claim 22, wherein: the holding structure is adjustablyconnected to the support structure in the area of the supporting point;and the adjustment unit is actively controllable.
 24. The optical deviceof claim 22, wherein: the supporting point comprises a first supportingpoint; the holding structure supports the optical element in an area ofa second supporting point; and the second supporting point is located inthe area of the first supporting point.
 25. The optical device of claim21, wherein: the holding device supports the optical element via aholding unit in a supporting direction; and the holding unit is formedto be substantially rigid in the supporting direction.
 26. The opticaldevice of claim 25, wherein: the holding unit comprises an activepositioning unit; and the holding unit is configured to adjust aposition of the optical element and/or an orientation of the opticalelement.
 27. The optical device of claim 21, wherein: the plurality ofdeformation units comprises a first deformation unit; the firstdeformation unit is configured to impose a deformation force in adeformation direction on the optical element; and the first deformationunit comprises an actuator unit configured to generate the deformationforce.
 28. The optical device of claim 27, wherein: the actuator unit isconfigured to generate a force in an actuation direction or a momentumin an actuation direction; and the actuator unit has a high rigidity inthe actuation direction.
 29. The optical device of claim 28, furthercomprising a transmission element disposed in a force flux between theactuator unit and the optical element, wherein: the transmission elementhas a low rigidity in a direction of force; the transmission element hasa rigidity in the actuation direction, which is related to the locationof the actuator unit; and the rigidity of the transmission elementcorresponds to at most 1% of the rigidity of the actuator unit in theactuation direction.
 30. The optical device of claim 28, wherein: theholding device comprises a holding structure that supports the opticalelement; the actuator unit is supported on the holding structure in theactuation direction; the holding structure has a rigidity in theactuation direction, which is related to the location of the actuatorunit; and the rigidity of the holding structure corresponds to at least5% to 10% of the rigidity of the actuator unit in the actuationdirection.
 31. The optical device of claim 21, wherein: the holdingdevice comprises a holding structure that holds the optical element; thedeformation units contact the holding structure; a measuring device isprovided which comprises a reference structure connected to the holdingstructure and a measuring unit; the measuring unit is configured tocapture a measurement value representative of a distance between thereference structure and a measuring point of the optical element; andthe measuring device is configured to determine, based on the firstmeasurement value, a detection value representative of a deformation ofthe optical element.
 32. The optical device of claim 31, wherein: thesupport structure supports the optical module in an area of a firstsupporting point; the holding structure supports the measuring device inthe area of a second supporting point; and the second supporting pointis located in the area of first supporting point.
 33. The optical deviceof claim 31, wherein: a deformation unit is configured to impose adisplacement on the optical element in a deformation direction; and thedeformation unit has a high rigidity in the deformation direction. 34.The optical device of claim 22, wherein: the deformation devicecomprises a separate abutment structure which is fixed to the holdingstructure; and a deformation unit is supported on the abutmentstructure.
 35. An optical imaging device, comprising: an illuminationdevice comprising an optical device according to claim 1, theillumination device configured to illuminate a pattern; and a projectiondevice comprising an optical element group configured image theilluminated pattern onto an object.
 36. A method, comprising: replacablyholding a microlithography optical element with a holding device of anoptical module, the optical module supported by a support structure; andimposing a pre-defined deformation on the microlithography opticalelement via a plurality of active deformation units.
 37. The method ofclaim 36, wherein the holding device is adjustably connected to thesupport structure in an area of a supporting point via an adjustmentunit that is actively controllable.
 38. The method of claim 36, wherein:the microlithography optical element is supported by a holding unit ofthe holding device in a supporting direction; and the holding unit issubstantially rigid in the supporting direction.
 39. The method of claim38, wherein: the holding unit comprises an active positioning unit; andthe holding unit adjusts a position of the microlithography opticalelement and/or an orientation of the microlithography optical element.40. The method of claim 36, wherein: the holding device comprises aholding structure that holds the optical element; the deformation unitscontact the holding structure; a measuring unit is provided whichincludes a reference structure connected to the holding structure and ameasuring unit; the measuring unit captures a measurement valuerepresentative of a distance between the reference structure and ameasuring point of the microlithography optical element; and themeasuring device determines, using the first measurement value, adetection value representative of a deformation of the of themicrolithography optical element.
 41. The method of claim 40, wherein: adeformation unit imposes a displacement on the optical element in adeformation direction; and the deformation unit has a high rigidity inthe deformation direction.
 42. The method of claim 36, wherein: thedeformation device comprises a separate abutment structure fixed to theholding structure; and a deformation unit is supported on the abutmentstructure.
 43. A set of components for an optical device, comprising: anoptical module comprising an optical element and a holding device; asupport structure; and an optical replacement module, wherein: thesupport structure supports the optical module in a first condition ofthe optical device; the holding device holds the optical element; theholding device comprises a deformation device comprising a plurality ofactive deformation units contacting the optical element; the pluralityof deformation units are configured to impose a pre-defined deformationon the optical element; the optical module is fixed to the supportstructure in a replaceable manner via a supporting point; the opticalreplacement module is configured to take the place of the optical modulein a second condition of the optical device and to be fixed to thesupport structure via the at least one supporting point.
 44. The set ofcomponents of claim 43, wherein: the optical replacement modulecomprises a further microlithography optical element and a furtherholding device; the further holding device holds the further opticalelement; the further holding device comprises a further deformationdevice comprising a plurality of further active deformation unitscontacting the further optical element; and the plurality of furtheractive deformation units are configured to impose a pre-defineddeformation on the further optical element.